Wendel bollman



iTED `sri-urns PATENTN oirFicE.

WENDEL BOLLMAN, OF BALTIMORE, MARYLAND.

CONSTRUCTION OF BRIDGES. I

`Specicaton of Letters Patent No. 8,624, dated January 6, 1852.

To all whom t may concern Be it known that I, WENDEL BOLLMAN, ofBaltimore, in the county of Baltimore and State of Maryland, haveinvented certain new and useful Improvements in Bridges, and that thefollowing is a full, clear, and exact description of the principle orcharacter which distinguishes them from all other things before knownand of the usual manner of making, modifying, and using the saine,reference being had to the accompanying drawing, making a part ther-eof.

My improvement consists in the mode of bracing bridges and constructingthetrusses, by which I carry the whole load upon the bridge, at anygiven point at t-he center or either side thereof directly back to theabutments, and at the-same time retain'all the forces of thrust andtension within the truss frame, restingthe weight merely upon abutmentsor piers, without any anchors or other similar device.

The-construction is as follows: I prepare a cast iron structure (a) (orthe stretcher may be made of wood when that material is to be used); ifof cast iron I prefer to make it a hollow tube, cast in sections ofproper length, and securely fastened in the manner shown at (b) in thedrawing; at sufficient intervals'I place a cast iron or wooden strutpendent from and securely aliiXed to the stretcher UL); at the bottom ofeach strut there is a recess (0'), into which lits a shoe (d), which hasspace` enough to slide longitudinally of-the frame; this shoe has arecess of semicircular form into which an eye bolt fits standing outfrom either side, by'means of which it is connected with tensionrods(e), that run from this point; at the bottom of the strut in a straightline, up to the end of the struc- `ture at the abutment; one tensionrod, or V'pair of tension rods, being carried up to each abutment; eachstrut is furnished with 1ndependent tension rods (e), that lead directlyback to the abutment, where they are connected with the ends of thestretcher. It will thus be seen that any loadrthat each and every one ofthe struts are required to bear, will be directly transferred to theabutment, without the intermediate action of any other strut or tensionrod; and the longitudinal force is resisted'by t-he stretcher withoutbringing any lateral strain upon the abutment. The sliding shoe (el)will be free to move on the foot of the strut to compensate for anyunequal expansion in the tension rods and stretchers. To steady the`struts in their upright position, braces or -prevent the stretcher fromrising at one point `when a heavy weight is thrown on to another, Iemploy diagonal rods (h), eX- tending from the top of each strut oneither side down to the bottom of the next adjacent strut. Thesediagonal rods not only give greater stability `to' the bridge, but they,also serve as an additional security to the bridge, in case the tensionrods, in case of a fiaw, should be ruptured, in which case the diagonalscarry back the weight to the I strut on either side, and divide the loadbetween them. Horizontal diagonal rods (i) `should be introduced, andwhere the road way is above the stretchers, as in Figure l,

there may be cross braces (7c) in the vertical 80 cross section: thefloor cross ties (m), are connected, as shown in the drawing, or in anylother convenient way. If the road way is at the bottom of the struts,yas in Fig. 3, then the diagonal cross braces (k) must Ybe omitted, andin place of the sliding shoe above named, there may be a short boltattached to t-he lower end of the strut, as seen in Figs. 3 and 4, thathave theequivalent to the shoe, with the further advantage of furnishling a convenient mode of connecting the road way wit-h the side frame. A

This bridge has the advantage of great strength and perfect security,with very little weight of metal; all the forces can be calculated withabsolute certainty, and without complicating the problem; and thestructure is so simple, that all the wrought iron work can be executedby the commonest blacksmith. The bridge has been thoroughly tested, andfully proves the correctness of the principles upon which it is based.

Having thus fully described my improved construction of bridges, what Iclaim therein as new, and Which I desire to secure by Lei:-v tersPatent, is f The combination of the tension rods e connecting t-he footof each strut with each end of the stretcher, substantially asdescribed, by which an independent support is given to the strut carriedback directly to the abutment, While at the same time no lateral forceor strain is brought upon the abut-ment, as herein fully set forth.

WENDEL BOLLMAN. VVitnesSes:v

B. W. BOTELER, JOHN H. MCMACHEN.

